Various catalyzed dehydrogenation, disproportionation and dehydrogenation steps have been existent in the prior art for many years. This invention brings a selective controlled sequence of these known steps at relatively mild treating conditions to convert cycloparaffinic material to aliphatic paraffinic material with the substantial exclusion of conversion to lower boiling compounds of other hydrocarbon materials present in the diesel fuel, aviation turbine fuel or kerosene.
A process for the dehydrogenation of cyclic paraffins is described in U.S. Pat. No. 3,290,406 issued to Pfefferle to produce olefins or diolefins from the dehydrogenation. A selective permeable membrane acts to keep hydrogen partial pressure in the dehydrogenation zone low and therefore increase the rate of dehydrogenation at lower temperatures. While this patent teaches general dehydrogenation over a catalyst, there is no mention of combining this dehydrogenation with disportionation and re-hydrogenation to acquire aliphatic paraffinic materials from naphthenic materials. A combination of naphtha cracking (pyrolysis), olefin disproportionation and olefinic dehydrogenation is taught in U.S. Pat. No. 3,345,285 issued to Hutt et al, wherein a naphtha is converted to ethylene, butadiene and gasoline by naphtha cracking, olefin disproportionation and then olefin dehydrogenation to the diolefinic material. This prior art process applies to the dehydrogenation of a C.sub.4 olefin, not to a cycloparaffin, and is applied to a finishing step, not as a feed preparation to a disproportionation step. One significant teaching in this reference is that ethylene is preferred to be used in a disproportionation reaction. However, ethane and methane mixed with hydrogen can be used in place of the ethylene in the disproportionation step. This is similar to applicant's feed material for the disproportionation step and is herein incorporated by reference to exemplify a specific type of olefin-acting material as therein taught.
In Sinfelt, U.S. Pat. No. 3,791,961, aromatics are produced from naphthenes by a dual catalyst system whereby naphthenes are dehydrogenated in an initial reaction zone while a second zone converts paraffins, along with dealkylation of alkyl benzenes, to acquire additional aromatic hydrocarbons. In this disclosure, the dual catalyst converts aliphatics and cyclic paraffins to aromatics. A combination dehydrogenation and disproportionation catalyst has been taught to function in a single reaction vessel such as described in U.S. Pat. No. 3,445,541, issued to Heckelsberg et al, wherein propane is used to prepare an olefin feed for disproportionation. This teaching is significant in the showing that disproportionation and dehydrogenation can, if desired, occur in a single vessel, however, the dehydrogenation of this prior disclosure is reserved to acyclic hydrocarbons, i.e. they do not concern the function of a ring opening material. Another olefin disproportionation reaction concerning acyclic materials is shown in U.S. Pat. No. 3,281,351 issued to Gilliland et al, for the conversion of propylene to ethylene and butylene with the latter being dehydrogenated to butadiene. Preliminary dehydrogenation and subsequent hydrogenation function of the instant invention concerning the conversion of cycloparaffinic materials to aliphatic paraffinic materials is not disclosed. A homogeneous catalyst for the disproportionation of olefins is described in U.S. Pat. No. 3,641,174, issued to Lyons, but does not refer to a ring opening reaction, in order to guarantee the patentee's disproportionation. For example, the patentee begins the reaction with a cyclic diolefin material to produce an aromatic material and a monoolefinic cyclic material. In contrast, the instant invention begins, in the disproportionation reaction, with ethylene and a cyclic monoolefin to arrive at an acyclic di-.alpha.-olefin. None of the instant disproportionation reactions actually refer to a selective ring opening function, especially one acting on a cyclic monoolefinic material derived from the dehydrogenation of a naphthene.